Conical omni-directional coverage multibeam antenna

Abstract

An omni directional coverage multibeam antenna relief on a ground surface having simple conical shapes to provide beam steering. One advantage of such a system is that the projected area is always constant and broadside to the intended direction resulting in limited scan loss effects. In the case of a cylinder as the conical shape, z-axis symmetry provides a constant antenna aperture projection in any azimuthal direction. Using this geometry, high level, side lobes are reduced considerably because of the natural aperture tapering from dispersion effects. Coverage area and power can be controlled by changing the ground surface angle and by selectively activating different antenna beam positions around the circumference of the ground surface, and by selectively changing the phase relationship between a given set of antenna beams.

What is claimed is:  
     
       1. An antenna system having a plurality of radiating structures spaced circumferentially around a center point, each radiating structure spaced equidistant from and parallel to a next adjacent radiating structure, said system comprising: 
       a ground surface circumferentially located around said center point and between said center point and each of said radiating structures, wherein the radius of the ground surface and the radius of the circumferentially spaced radiating structures are selected to cooperatively control side lobe levels; and  
       means for phase shifting a transmission signal from certain activated ones of said activated radiating structures a selected delay amount, the phase shift amount being selected such that the transmission signal wave front leaving said certain activated radiating structures is in a relatively straight line substantially perpendicular to the direction of travel of said transmission signal, the direction of travel being normal to a point on the ground surface corresponding to one of said certain activated radiating structures.  
     
     
       2. The antenna system set forth in claim  1  wherein each said radiating structure includes a plurality of individual radiation points. 
     
     
       3. The antenna system set forth in claim  2  wherein certain of said radiation points are dipole antennas. 
     
     
       4. The antenna system set forth in claim  2  wherein certain of said radiation points are patch antennas. 
     
     
       5. The antenna system set forth in claim  2  wherein certain of said radiation points are helical antennas. 
     
     
       6. The antenna system set forth in claim  2  wherein the phase relationship between each of the individual radiation points of a particular radiation structure is adjustable. 
     
     
       7. The antenna system set forth in claim  2  wherein said radiation points are angled with respect to each other. 
     
     
       8. The antenna system set forth in claim  1  wherein said phase shift means for each said radiating structure includes first and second delay devices, for establishing a specific phase relationship between respective radiating points of said radiating structure. 
     
     
       9. The antenna system set forth in claim  1  wherein the number of said certain activated radiating structures for any given transmission is selectively controllable. 
     
     
       10. The antenna system set forth in claim  1  wherein the one of said certain activated radiating structures which is used as the point to measure the direction of wave front travel is selectable. 
     
     
       11. The antenna system set forth in claim  1  wherein the radius of the circumferentially spaced structures is λ/4±λ/8 above and normal to the ground surface. 
     
     
       12. The antenna system set forth in claim  1  wherein the distance between adjacent ones of said plurality of radiating structures is ≦⅘λ. 
     
     
       13. The antenna system set forth in claim  1  wherein the ground surface has a top and a bottom edge and wherein each of these edges is rounded inward to form a side lobe suppressor torus. 
     
     
       14. The antenna system set forth in claim  13  wherein at least one of the rounded edges of the ground surface includes signal absorption means. 
     
     
       15. The antenna system set forth in claim  1  wherein the ground surface is at an angle with respect to the vertical. 
     
     
       16. The antenna system set forth in claim  15  wherein the ground surface has a top and a bottom edge and wherein the angle causes the bottom edge of the ground surface to be closer to the center point than the top edge of the ground surface. 
     
     
       17. The antenna system set forth in claim  15  wherein the angle is between 0° and 45° from the vertical. 
     
     
       18. The antenna system set forth in claim  15  wherein the angle is selectable from time to time during operation. 
     
     
       19. The antenna system set forth in claim  1  wherein said radiation structures create circular polarization of a transmission signal. 
     
     
       20. The antenna system set forth in claim  1  wherein the activation of any one structure involves the activation of at least two adjacent structures. 
     
     
       21. The antenna system set forth in claim  20  wherein said at least two adjacent structures are controlled using Wilkinson and hybrid combiners in a non-interleaved mode with a loss of 3 dB of power. 
     
     
       22. The antenna system set forth in claim  20  wherein said at least two adjacent structures are controlled using Wilkinson and hybrid combiners in an interleaved mode with no loss of power. 
     
     
       23. The antenna system set forth in claim  22  wherein said interleaved mode includes a dual antenna array for each of the structures. 
     
     
       24. The antenna system set forth in claim  23  wherein each of the dual antennas of each structure includes a plurality of individual radiator points, oriented to create an elliptical radiation pattern. 
     
     
       25. The antenna system set forth in claim  24  wherein the elliptical radiation pattern is circular. 
     
     
       26. The method of operating an antenna system having a plurality of radiating structures spaced circumferentially around a center point, each radiating structure spaced equidistant from and parallel to a next adjacent radiating structure, wherein a ground surface is circumferentially located around the center point and between the center point and each of the radiating structures; the method comprising the steps of: 
       delaying a transmission signal from certain activated ones of the radiating structures a selected delay amount; and  
       selecting the delay amount such that the transmission signal wave front leaving the certain activated ones of the radiating structures is in a relatively straight line substantially perpendicular to the direction of desired travel of the transmission signal, the delay amount also being selected to produce a tapered aperture distribution when the certain activated ones of the radiating structures are driven substantially at unity.  
     
     
       27. The method set forth in claim  26  further including the step of selectively controlling the number of activated radiating structures for any given transmission. 
     
     
       28. The method set forth in claim  27  further including the step of selecting the one of the activated radiating structures which is used as the point to measure the direction of wave front travel. 
     
     
       29. The method set forth in claim  26  wherein the ground surface has a top and a bottom edge, said method further including the step of positioning the bottom edge of the ground surface to be closer to the center point than is the top edge of the ground surface. 
     
     
       30. The method set forth in claim  26  further comprising the step of: 
       selecting, during operation, a scan angle in the elevation plane.  
     
     
       31. The method set forth in claim  30  wherein each radiating structure includes a plurality of individual sub-radiating structures, and wherein the step of selecting a scan angle in the elevation plane includes the step of: 
       adjusting the phase relationship of a signal radiating from the individual sub-radiating structures of each radiating structure.  
     
     
       32. The method of operating an antenna system having a plurality of transmitting structures spaced circumferentially around a center point, each such structure spaced equidistant from and parallel to a next adjacent structure, wherein a ground surface is circumferentially located around the center point and between the center point and each of the structures; the method comprising the steps of: 
       delaying a reception signal from certain activated ones of the structures a selected delay amount; and  
       selecting the delay amount such that the reception signal wave front arriving at the certain activated ones of the structures is in a relatively straight line substantially perpendicular to the direction from which the transmission signal was originated, the delay amount also being selected to produce a tapered aperture distribution when the certain activated ones of the structures are driven substantially at unity.  
     
     
       33. The method set forth in claim  32  further including the step of selectively controlling the number of activated radiating structures for any given transmission. 
     
     
       34. The method set forth in claim  33  further including the step of selecting the one of the activated structures which is used as the point to measure the direction of wave front travel. 
     
     
       35. The method set forth in claim  32  wherein the ground surface has a top and a bottom edge and wherein each of these edges is rounded inward to form a side lobe suppressor torus. 
     
     
       36. The method set forth in claim  32  wherein the ground surface has a top and a bottom edge, said method further including the step of positioning the bottom edge of the ground surface to be closer to the center point than is the top edge of the ground surface. 
     
     
       37. The method of constructing an antenna system comprising the steps of: 
       establishing a ground surface circumferentially located around a mast, said ground surface circumscribing a volume substantially perpendicular to a surface upon which signals transmitted from a radiating structure are to be received on; and  
       positioning a plurality of antenna structures at spaced intervals circumferentially around the ground surface, wherein a radius of the ground surface and a radius of the circumferentially spaced antenna structures are selected to provide a selected divergence factor; and  
       associating with each antenna structure a delay device for controlling the phase of a signal through the associated antenna with respect to other ones of the antenna structures.  
     
     
       38. The method set forth in claim  37  wherein the ground surface is a truncated cone having an angle Θ with respect to the signal receiving surface. 
     
     
       39. The method set forth in claim  38  further including the step of adjusting the angle Θ in accordance with desired signal receiving surface area coverage. 
     
     
       40. The method set forth in claim  38  further including the step of: 
       curving either the top or bottom edge of the ground surface or both to form a torus.  
     
     
       41. The method set forth in claim  40  further including the step of adding lossy material to the torus. 
     
     
       42. The method set forth in claim  37  further including the step of constructing at least some of the antenna structures as signal receiving structures and some as signal transmission structures. 
     
     
       43. The method set forth in claim  42  further including the step of forming two RF chambers within the volume of the ground surface, one chamber for containing the receiving structures and one chamber containing the transmission structures. 
     
     
       44. The method set forth in claim  43  wherein both chambers are contained within a single radome, all supported by the mast extending through the longitudinal center of the antenna system. 
     
     
       45. The method set forth in claim  37  wherein certain of the radiating structures have a first design and others of the radiating structures have a second design. 
     
     
       46. The method set forth in claim  37  wherein each antenna structure is parallel to the longitudinal axis of the ground surface. 
     
     
       47. The method set forth in claim  46  further including the step of constructing a plurality of individual antenna structures connected to a common signal transmission medium. 
     
     
       48. The method set forth in claim  47  further including the step of adjusting the antenna structures which are connected to a common medium so as to be in phase with each other. 
     
     
       49. The method set forth in claim  48  further including the step of adjusting the antenna structures, which are connected to a common medium so as to be out of phase with each other by a selected amount. 
     
     
       50. The method set forth in claim  37  wherein said radiation structures create circular polarization of a transmission signal. 
     
     
       51. The method set forth in claim  37  wherein the activation of any one structure involves the activation of only four adjacent structures. 
     
     
       52. The method set forth in claim  51  wherein said four adjacent structures are controlled using Wilkinson and hybrid combiners in a non-interleaved mode with a loss of 3 db of power. 
     
     
       53. The method set forth in claim  51  wherein said four adjacent structures are controlled using Wilkinson and hybrid combiners in an interleaved mode with no loss of power. 
     
     
       54. The method set forth in claim  53  wherein said interleaved mode includes a dual antenna array for each of the structures. 
     
     
       55. The method set forth in claim  54  wherein each of the dual antennas of each structure includes a plurality of individual radiator points, oriented to create an elliptical radiation pattern. 
     
     
       56. The method set forth in claim  55  wherein the elliptical radiation pattern is circular.